Door closers are used to automatically close doors; hold doors open for short intervals, and control opening/closing speeds in order to facilitate passage through a doorway and to help ensure that doors are not inadvertently left open. A door closer is often attached to the top or bottom of a door, and when the door is opened and released, the door closer generates a mechanical force that causes the door to automatically close without any user input. Thus, a user may open a door and pass through its doorway without manually closing the door.
Many conventional door closers are designed to apply varying forces to a door as a function of the door angle (i.e., the angle at which the door is open). In this regard, when the door is first opened, the door closer is designed to generate a relatively small force, which tends to push the door closed, so that the door closer does not generate significant resistance to the user's efforts to open the door. However, as the door is further opened thereby increasing the door angle, greater force is applied to the door by the door closer at various predefined door angles.
Many conventional door closers are mechanically actuated and have a plurality of valves, a spring, and a movable element for controlling the varying amounts of force applied to the door as a function of door angle, as described above. A typical door closer may use a piston that moves through a reservoir filled with a hydraulic fluid, such as oil. The piston serves as the movable element to counter the force of the spring. Adjusting the valve settings in such a conventional door closer can be difficult and problematic since closing times and forces can vary depending on temperature, pressure, wear and installation configuration. Moreover, adjusting the valve settings in order to achieve a desired closing profile for a door can be burdensome for at least some users. Many door closers exhibit much less than ideal closing characteristics because users are either unwilling or unable to adjust and re-adjust the valve settings in a desired manner or are unaware that the settings can be changed in order to effectuate a desired closing profile in the face of temperature changes, wear over time and/or modifications to the physical installation.